Additionally, many brain areas of central interest to reward researchers (e.g., the NAcc, orbital frontal cortex, and MPFC) lie near tissue boundaries (i.e., next to ventricles and sinuses), which can cause artifacts unless care is taken to minimize magnetic inhomogeneities (e.g., by use of special pulse sequences or acquisition parameters).
Relative to PET, however, fMRI affords increased spatial resolution (e.g., as small as 1 mm 3 versus 8 mm 3 ) and, importantly, substantially increased temporal resolution (e.g., seconds rather than minutes). fMRI also has advantages of safety and convenience – since blood itself provides the signal, researchers need not inject radioactive compounds or other agents into subjects prior to scanning.
These advantages have made FMRI one of the most popular methods for visualizing changes in the activation of small subcortical structures. Shortly after its development, researchers began to use fMRI to examine neural responses to both primary (e.g., touch, juice, food, odors) and secondary (e.g., money) incentives. Primary and secondary incentives have yielded overlapping patterns of activation, but the extent of their similarity has not yet been fully characterized (see Chapter 24 of this volume; O’Doherty, 2004 ). Based on their direct relevance to neuroeconomic questions, we focus here on studies that utilized monetary incentives. Adopting a successful strategy from fMRI studies of vision research, initial fMRI studies attempted to “ localize ” or correlate regionally specific patterns of brain activation with responses to monetary incentives in the absence of choice.
In an initial fMRI study utilizing a cued reaction-time task, trials involving monetary gain or loss activated striatal regions (including caudate and putamen) as well as other mesolimbic and motor regions (i.e., insula, MPFC, supplementary motor area, and motor cortex), relative to identical trials that lacked monetary incentives ( Knutson et al ., 2000 ). Trials involving monetary loss additionally activated anterior thalamus and anterior cingulate.
Barry Demp Coaching
